Geologic maps serve as a valuable tool in resource exploration.Traditional mapping is characterized by time-intensive and high-cost fieldwork, but through multispectral and hyperspectral remotely sensed images it is possible to map extensive areas instantly.

Geologic background of Marysvale volcanics

Bandpass Filters

Bandpass filters are essential for collection and analysis of satellite imagery, they allow specific ranges of electromagnetic wavelengths, or bands, to be transmitted while blocking others.

FWHM

Full Width Half Mass (FWHM) is an important concept for understanding how different bands are delineated.

The graph below visualizes the idea of FWHM. Each band in a spectral device only takes in a specific range of wavelengths, often the wavelength for each band is just denoted as the peak, but in reality each sensor is collecting a range of wavelengths. This is determined by denoting the FWHM as the area between the 50% transmittance on both sides of the curve.

Landsat 8, Hyperion, and ASTER bands

In this plot you can see all the bands for Landsat 8, Hyperion, and ASTER. With their FWHM denoted as boxes. Its important to point out how Landsat 8 does have a band in the Short Wave Infrared (SWIR), but the FWHM is wide and this means that any SWIR data saved for this band could be attributed to any wavelength inside of the FWHM.

Location of research

Geologic Map

Iron Oxides

Iron Oxides mapping can be created using Band4/Band2

Clay and Hydroxyl

Hydroxyl mineral mapping can be created using Band6/Band7

Ferrous

Ferrous (iron minerals) can be mapped using Band6/Band5

Sabins Ratio

A Sabins Ratio plot can be created by combining these three plots into an RGB profile.

Iron-oxide dominated areas are mapped in pink, clay and hydroxyl minerals in green and ferrous minerals are discriminated in blue. Hydrothermal alteration areas are represented by the association of green-pink or yellow zones.